Hydrotreating process

ABSTRACT

A hydrotreating catalyst comprises molybdenum, nickel, and phosphorus components supported on gamma alumina precalcined at a temperature of at least 1375 DEG  F.

This is a division of application Ser. No. 38,334, filed May 11, 1979,now U.S. Pat. No. 4,255,282, issued Mar. 10, 1981.

BACKGROUND AND SUMMARY OF THE INVENTION

This invention relates to a hydrotreating catalyst and a method for itspreparation. More particularly, the invention relates to a hydrotreatingcatalyst prepared from gamma alumina precalcined at a temperature above1375° F.

In the refining of liquid hydrocarbons derived from mineral oils andother sources, it is often necessary to subject the liquid hydrocarbonor fraction thereof to hydrotreating. Hydrotreating is a process forreducing the concentration of nitrogen and sulfur components in ahydrocarbon feedstock so that, when the product hydrocarbon iseventually combusted, less SO₂ and NO will form, and hence present lessof a pollution problem. In addition, it is often desirable to removenitrogen from such feedstocks in order to protect hydrocrackingcatalysts and the like which deactivate in the presence of nitrogen.

In general, hydrotreating is accomplished by contacting the feedstockcontaining nitrogen and/or sulfur with a catalyst in the presence ofhydrogen and under conditions, including elevated temperature andpressure, such that the sulfur components are converted to H₂ S and thenitrogen components to NH₃, both of which are separated from thedesulfurized and denitrogenated liquid product.

A typical hydrotreating catalyst comprises particles containing a GroupVIII active metal component and a Group VI active metal componentsupported on a refractory oxide such as alumina. Oftentimes, phosphoruscomponents are also present in the catalyst to improve its activity byincreasing its acidity. One catalyst which has been successfullyemployed on a commercial basis consists essentially of molybdenum,nickel, and phosphorus components supported on gamma alumina. A typicalpreparation procedure for such a catalyst is as follows: particles ofhydrated alumina are firstly formed into a desired size and shape byextruding the hydrated alumina through a die having circular or cloverleaf-shaped openings therein and cutting the extruded matter intoparticles (or extrudates) of 1/16-1/2 inch lengths. After calcining at atemperature of about 1150°-1250° F., the resulting gamma aluminaextrudates are in a condition to be contacted with an impregnatingsolution comprising dissolved salts of molybdenum and nickel inphosphoric acid. The impregnated extrudates (or composites) are thensubjected to a final calcination at a temperature around 900° F. toconvert the impregnated metals to their oxide forms.

Quite unexpectedly, it has now been found that, if the above procedureis only slightly altered, the resulting catalyst is substantially moreactive for hydrotreating purposes. More specifically, it has been foundthat, if the first calcination, usually termed the precalcination, isconducted at a temperature of at least 1375° F., and preferably at1450°-1600° F., then the final catalyst will have increased activity forremoving sulfur and nitrogen components from liquid hydrocarbons undertypical hydrotreating conditions.

In one embodiment, the invention comprises a hydrotreating catalystcomposition comprising molybdenum, nickel, and phosphorus componentssupported on gamma alumina prepared by a method including the step ofimpregnating a support comprising gamma alumina precalcined at atemperature of at least 1375° F. with components of nickel, phosphorus,and molybdenum. In an alternative embodiment, the invention comprises amethod for preparing a hydrotreating catalyst wherein particles of gammaalumina precalcined at at least 1375° F. are impregnated with a solutioncomprising phosphoric acid containing dissolved nickel and molybdenumcomponents, and the resulting composite is calcined at an elevatedtemperature. In yet another embodiment, the invention comprises animproved hydrotreating process wherein the improvement resides in theuse of a catalyst prepared by calcining a composite comprisingmolybdenum, nickel, and phosphorus components impregnated into gammaalumina precalcined at at least 1375° F. Usual precalcinationtemperatures herein are above 1400° F.

DETAILED DESCRIPTION OF THE INVENTION

In accordance with this invention, a catalyst suitable for hydrotreatingpurposes is prepared by contacting gamma alumina particles precalcinedat a temperature of at least 1375° F., preferably at least 1450° F.,with a suitable impregnating solution or solutions known in the art asuseful for incorporating molybdenum, nickel, and phosphorus componentswith gamma alumina. A preferred impregnating solution consists of anaqueous solution of phosphoric acid, ammonium heptamolybdate, and nickelnitrate. Depending upon the proportion of nickel, molybdenum, andphosphorus desired in the final catalyst, the impregnating solutioncontains molybdenum in a concentration of 10-30 wt.% as MoO₃, nickel ina concentration of 1-10 wt.% as NiO, and phosphorus in a concentrationof 1-10 wt.% P. After the gamma alumina particles have been contactedfor a sufficient time with the impregnating solution to insure fullimpregnation of the desired amount of nickel, molybdenum, andphosphorus, it is dried and subjected to a final calcination, usually ata temperature in the 800°-1000° F. range. The catalyst is thenpresulfided, either by contact at an elevated temperature with an H₂ andH₂ S-containing gas stream or in situ by allowing the sulfur in thehydrocarbon feedstock to gradually convert the oxide components to thesulfide form. The final catalyst preferably comprises 14-25 wt.%molybdenum components (calculated as MoO₃), 2.0-6.0 wt.% nickelcomponents (calculated as NiO), and 2.0-6.0 wt.% phosphorus components(calculated as P). Most preferably, the ratio of nickel components asNiO to molybdenum components as MoO₂ is between about 0.18:1 and 0.19:1,and the ratio of phosphorus components as F to nickel components as NiOis about 1:1. Suitable catalysts comprise 12-30 wt.% molybdenumcomponents (calculated as MoO₃).

It is a critical feature of the invention herein that the gamma aluminasupport material be precalcined at at least 1375° F., preferably at atleast 1450° F., prior to contact with one or more impregnatingsolutions. In one embodiment of the invention, the precalcination iscarried out by subjecting a hydrated alumina (Al₂ O₃.xH₂ O) to atemperature in the range of 1375°-1800° F., preferably 1450°-1600° F.,for an extended time period, usually 1/4-5 hours, preferably 1/2-2hours, in the presence of air or other environment consisting of gases(e.g., N₂, CO₂, Ar), which do not adversely affect the catalyst underhigh temperature conditions. Alternatively, the same calcinationprocedure may be applied to any gamma alumina that has never beensubjected to temperatures above 1375° F. for a significant length oftime. For example, there are many commercially available gamma aluminacatalyst supports which, during the manufacture thereof, are calcined inthe 800°-1300° F. range, and it is a specific embodiment of theinvention that such catalyst supports be calcined again at a temperatureabove 1375° F., the second calcination being considered herein as theprecalcination required prior to contact with an impregnating solution.

Catalysts prepared in accordance with the invention may be used tohydrotreat any hydrocarbon feedstock or fraction thereof containingsulfur and/or nitrogen components. Typical hydrocarbon feedstockssuitable for treatment herein are light and heavy gas oils, cycle oils,naphthas, kerosene, turbine fuels, diesel fuels and syncrudes such asshale oils. The preferred feedstocks are gas oils, in particular gasoils or vacuum gas oils having at least 50% of the components thereofboiling at temperatures less than 700° F., preferably less than 650° F.The typical gas oil to be treated by contact with the catalyst describedherein contains at least 2 ppmw of nitrogen components (calculated asnitrogen), usually 10-5000 ppmw of nitrogen components, and at least0.02% by weight of sulfur components (calculated as sulfur), usually1.0-3.0% by weight.

Hydrotreating with the catalysts herein is accomplished under conditionsknown in the art for denitrogenating and/or desulfurizing hydrocarbonfeedstocks in the presence of hydrogen. In the usual instance, thefeedstock is passed at an elevated temperature and pressure through acatalytic reactor containing a stationary bed of catalyst. Hydrogen isalso passed through the reactor with the feedstock, and the hydrogen notconsumed in converting the sulfur components to H₂ S and the nitrogencomponents to NH₃ is separated from the denitrogenated and/ordesulfurized product oil and recycled to the inlet of the reactor. Theconditions employed vary from feedstock to feedstock, but the range ofconditions set forth in the following table will be those typicallyemployed:

                  TABLE I                                                         ______________________________________                                                                          Most                                        Operating Conditions                                                                        Suitable  Preferred Preferred                                   ______________________________________                                        Temperature, °F.                                                                     400-1000  600-850   650-800                                     Pressure, PSIG                                                                              100-5000  400-3000   500-2000                                   Space Velocity, LHSV                                                                        0.1-15    1-10      2-7                                         Hydrogen Recycle Rate,                                                        cf/bbl.sup.1   400-20000                                                                              1000-15000                                                                               4000-10000                                 ______________________________________                                         .sup.1 Measured at 60° F. and 1 atmosphere                        

Although the conditions chosen for any given feedstock will depend inlarge measure upon the quality of the product desired and theconcentrations of sulfur and nitrogen in the feedstock, conditions areusually selected to remove a substantial proportion of both nitrogen andsulfur components, usually at least 50% of each and preferably at least80% of the sulfur components and 90% of the nitrogen components. Mostpreferably, conditions are chosen to reduce the nitrogen compoundsconcentration to less than 10 ppmw (as N) and the sulfur compoundsconcentration to less than 200 ppmw (as S).

The following comparative example is provided to illustrative theinvention; it is not intended to be limiting.

COMPARATIVE EXAMPLE

Several catalysts were prepared and tested under typical hydrotreatingconditions against a reference catalyst consisting of particles of acommercially available catalyst sold under the designation HCF by theAmerican Cyanamid Company. The HCF catalyst had a colver leafcross-sectional shape and was of nominal composition: 18 wt.% MoO₃, 2.9wt.% NiO, 3.2 wt.% P, and the balance gamma alumina. The five catalystscompared against the performance of this commercial catalysts wereprepared as follows:

Catalyst No. 1

To 30 g of ammonium heptamolybdate ((NH₄)₆ Mo₇ O₂₄.4H₂ O) were slowlyadded 7 ml of 85% phosphoric acid (H₃ PO₄) in the presence of sufficientwater that the resulting liquid volume was about 50 ml. The ammoniumheptamolybdate was allowed to fully dissolve in the liquid, and then 17g of nickel nitrate (Ni(NO₃)₂.6H₂ O) was added to the solution anddissolved. The resulting deeply green impregnating solution had a totalvolume of 73 ml.

One hundred grams of hydrated alumina extrudates having a size and shapeessentially identical to that of the HCF catalyst particles wereprecalcined for 1/2 hour at 1250° F. and then contacted with theimpregnating solution by pouring the solution into a beaker containingthe precalcined gamma alumina particles. After brief stirring to fullysaturate the pores, the alumina particles were aged for about 1 hour,oven dried overnight at 110° C., and calcined in flowing air at 900° F.for about one-half hour. Catalyst No. 1 had the following composition:18.0 wt.% MoO₃, 3.3 wt.% NiO, 2.6 wt.% P, gamma alumina the balance.

Catalyst Nos. 2 and 3

Catalyst Nos. 2 and 3 were prepared in a manner identical to No. 1except that the precalcination temperature was 1500° F. rather than1250° F. Catalysts No. 2 and 3 had the same composition as Catalyst No.1.

Catalyst No. 4

Catalyst No. 4 was prepared in a manner identical to that of CatalystsNos. 2 and 3 except that impregnation was accomplished as follows: 100ml of impregnating solution of the same composition as that describedabove for Catalysts Nos. 1-3 was prepared. It was heated to 40° C. andcontacted with the alumina particles for 1 minute, after which time theexcess liquid was separated on a Buchner funnel. The catalyst was agedless than 1 hour, and then oven dried and calcined as Catalyst Nos. 1through 3. Catalyst No. 4 had the following composition: 19.4 wt.% MoO₃,3.5 wt.% NiO, 3.8% P, gamma alumina the remainder.

Catalyst No. 5

This catalyst was prepared identically to Catalyst No. 4 except that theimpregnating solution consisted of 62 ml of the impregnating compositionused in preparing Catalyst No. 4 plus sufficient added water to producea total solution of 100 ml. Catalyst No. 5 had a composition as follows:15.1 wt.% MoO₃, 2.7 wt.% NiO, 3.0 wt.% P, gamma alumina the remainer.

Catalysts Nos. 1-5 and the HCF catalyst were then each presulfided bycontact with a gas stream consisting of 10 vol.% H hd 2S and 90 vol.%H₂. The temperature during the presulfiding was initially at roomtemperature and then was gradually increased hourly by 50° C. until 700°F. was reached. The 700° F. temperature was held for two hours.

Catalysts Nos. 1-5 were then each tested to determine their individualactivities for hydrodenitrogenation and hydrodesulfurization incomparison to the reference HCF catalyst. The catalysts were eachcharged to a reactor and twice (once at 700° F. and again at 720° F.)utilized to hydrotreat a gas oil feedstock having the characteristicsshown in Table I under the following conditions: 1400 psig totalpressure, 4.0 LHSV, and hydrogen rate of 6000 CFH/bbl (measured at 60°F. and 1 atmosphere). Giving the reference HCF catalyst an arbitraryactivity of 100, the relative activities of Catalyst Nos. 1 through 5compared to the HCF catalyst were determined by calculation andtabulated in Table II. These determinations were based on a comparisonof the reaction rates for denitrogenation and desulfurization obtainedfrom the data of the experiment according to the following standardequations which assume first order kinetics for denitrogenation and oneand a half order kinetics for desulfurization: ##EQU1## where N_(fr) andN_(pr) are the respective concentrations of nitrogen in the feed andproduct obtained with the reference catalyst and N_(f) and N_(P) are therespective concentrations of nitrogen in the feed and product obtainedwith a catalyst being compared to the reference, and ##EQU2## whereS_(fr) and S_(pr) are the respective concentrations of sulfur in thefeed and product obtained with the reference catalyst and S_(f) andS_(P) are the respective concentrations of sulfur in the feed andproduct obtained with a catalyst being compared to the reference.

                  TABLE II                                                        ______________________________________                                        FEEDSTOCK CHARACTERISTICS                                                     Boiling Range, °F.                                                     ______________________________________                                        IBP/5       250/460  Gravity, D287, °API                                                                   24.6                                      10/20       512/545  Sulfur, wt. %  1.33                                      30/40       577/600  Nitrogen:                                                50/60       626/664  Basic, wt. %   0.0738                                    70/80       691/725  Total, wt. %   0.1810                                    90/95       767/804  Pour Point, D-97, °F.                                                                 .443                                      EP/Rec., Vol. %                                                                           833/99.3 Carbon Residue on                                                             10% Botts, D-524,                                                             wt. %          0.32                                      ______________________________________                                    

                                      TABLE III                                   __________________________________________________________________________                           Relative Activities                                                           Basic   Total                                          Compos. wt. % Precalcination                                                                         Nitrogen                                                                              Nitrogen                                                                              Sulfur                                 Catalyst                                                                           MoO.sub.3                                                                         NiO                                                                              P Temperature, °F.                                                                700° F.                                                                    720° F.                                                                    700° F.                                                                    720° F.                                                                    700° F.                                                                    720° F.                     __________________________________________________________________________    Ref  18  2.9                                                                              3.2                                                                             1200° F.*                                                                       100 100 100 100 100 100                                No. 1                                                                              18  3.3                                                                              2.6                                                                             1250     102 112 104 106 100  88                                No. 2                                                                              18  3.3                                                                              2.6                                                                             1500     119 125 113 114 117 121                                No. 3                                                                              18  3.3                                                                              2.6                                                                             1500     121 126 118 120 118 124                                No. 4                                                                              19.4                                                                              3.5                                                                              3.3                                                                             1500     120 138 108 118 112 120                                No. 5                                                                              15.1                                                                              2.7                                                                              3.3                                                                             1500     110 119 105 108 117 114                                __________________________________________________________________________     *The support precalcination temperature of 1200° F. is believed to     be accurate; 1200° F. is typical precalcination temperature for        commercial hydrotreating catalysts.                                      

As shown by the results tabulated in Table II, Catalysts Nos. 2 through5, all of which were precalcined at 1500° F., evidenced higher activityin every category than both the HCF catalyst believed to have beenprecalcined at 1200° F. and Catalyst No. 1 which was known to have beenprecalcined at 1250° F. Even Catalyst No. 5, which had a low MoO₃content, exhibited higher activity than HCF or Catalyst No. 1.

In view of the foregoing, it should be apparent that the invention iscapable of many modifications, alterations, and variations. Accordingly,it is intended to embrace all such altertions, modifications, andvariations as fall within the spirit and scope of the appended claims.

I claim:
 1. In a method for hydrotreating a hydrocarbon feedstockcontaining one or more components selected from the group consisting oforganonitrogen compounds and organosulfur compounds wherein thehydrocarbon feedstock is contacted with a catalyst in the presence ofhydrogen under sufficient conditions of elevated temperature andpressure to reduce the total content of organonitrogen compounds plusorganosulfur compounds in the feedstock, and wherein said catalyst isprepared by impregnating gamma alumina with a phosphoric acid solutioncontaining dissolved nickel and molybdenum components followed bycalcining at an elevated temperature, the improvement wherein prior toimpregnation said gamma alumina is precalcined at a temperature of atleast 1375° F.
 2. The method of claim 1 wherein said catalyst wasprepared with gamma alumina particles precalcined at a temperature above1400° F.
 3. The method of claim 2 wherein said catalyst comprises 12-30wt.% of one or more molybdenum components, calculated as MoO₃, 2-6 wt.%of one or more nickel components, calculated as NiO, and 2-6 wt.% of oneor more phosphorus components, calculated as P, and the remainderconsists essentially of gamma alumina.
 4. The method of claim 3 whereinsaid catalyst was prepared with gamma alumina particles precalcined at atemperature above 1450° F.
 5. In a hydrotreating process wherein ahydrocarbon feedstock containing one or more contaminants selected fromthe group consisting of organosulfur compounds and organonitrogencompounds is contacted with a catalyst in the presence of hydrogen andunder conditions of elevated temperature and pressure such that asubstantial proportion of said contaminants are removed, the improvementwherein said catalyst comprises molybdenum, nickel, and phosphoruscomponents supported on gamma alumina, said catalyst having beenprepared by a method comprising the steps of impregnating a supportcomprising gamma alumina precalcined at a temperature of at least 1375°F. with components of molybdenum, nickel, and phosphorus, and calciningthe resulting composite at an elevated temperature.
 6. A hydrotreatingprocess as defined in claim 5 wherein said gamma alumina is precalcinedat a temperature of at least 1450° F.
 7. A hydrotreating process asdefined in claim 5 wherein said gamma alumina is precalcined at atemperature less than 1800° F.
 8. A hydrotreating process as defined inclaim 5 wherein said gamma alumina is precalcined at a temperaturebetween about 1450° and 1600° F.
 9. A hydrotreating process as definedin claim 5, 6, 7, and 8 wherein said catalyst composition comprises 12to 30 wt.% of one or more molybdenum components, calculated as MoO₃, 2to 6 wt.% of one or more nickel components, calculated as NiO, 2 to 6wt.% of one or more phosphorus components, calculated as P, and theremainder consisting essentially of gamma alumina.
 10. A hydrotreatingprocess comprising contacting a hydrocarbon feedstock containingorganoitrogen compounds with a solid, particulate catalyst in thepresence of hydrogen and at a temperature between about 600° and 850° F.and at a pressure between about 400 and 3000 psig and at a spacevelocity between about 1 and 10 LHSV so as to substantially lower theorganonitrogen content of said feedstock by conversion to ammonia, saidcatalyst containing molybdenum, nickel, and phosphorus componentssupported on gamma alumina in proportions sufficient to be catalyticallyactive for hydrotreating purposes, said catalyst having been prepared bya method comprising the steps of (1) precalcining at a temperature above1375° F. but less than 1800° F. a substance selected from the groupconsisting of hydrated alumina and gamma alumina previously calcined ata temperature less than 1375° F., said precalcining being underconditions producing an alumina product consisting essentially of gammaalumina precalcined above 1375° F., (2) impregnating said aluminaproduct with a phosphoric acid solution containing dissolved molybdenumand nickel components, and (3) calcining the resulting composite at atemperature above about 800° F.
 11. A hydrotreating process as definedin claim 10 wherein said precalcining in step (1) is carried out at atemperature between 1450° and 1600° F.
 12. A hydrotreating process asdefined in claim 10 or 11 wherein said catalyst composition comprises 12to 30 wt.% of one or more molybdenum components, calculated as MoO₃, 2to 6 wt.% of one or more nickel components, calculated as NiO, 2 to 6wt.% of one or more phosphorus components, calculated as P, and theremainder consisting essentially of gamma alumina.
 13. A hydrotreatingprocess as defined in claim 12 wherein said hydrocarbon feedstock alsocontains organosulfur compounds, which organosulfur compounds areremoved in a substantial proportion during said contacting by conversionto hydrogen sulfide.
 14. A hydrotreating process comprising contacting ahydrocarbon feedstock containing organonitrogen and organosulfurcompounds with a particulate, solid catalyst in the presence of hydrogenand at a temperature between about 650° and 800° F. and at a pressurebetween about 500 and 2000 psig and at a space velocity between about 2and 7 LHSV so as to substantially lower the content of organonitrogenand organosulfur compounds in said feedstock by conversion to ammoniaand hydrogen sulfide, respectively, said catalyst having been preparedby a method comprising the steps of (1) precalcining at a temperature inthe range of 1450° to 1550° F. a substance selected from the groupconsisting of hydrated alumina and gamma alumina previously calcined ata temperature no greater than 1375° F., (2) impregnating the resultingprecalcined gamma alumina with a phosphoric acid solution containingdissolved molybdenum and nickel components, said impregnation being suchthat the resulting composite contains sufficient molybdenum, nickel, andphosphorus components to produce during the calcination of step (3) afinal catalyst containing 12 to 30 wt.% of one or more molybdenumcomponents, calculated as MoO₃, 2 to 6 wt.% of one or more nickelcomponents, calculated as NiO, and 2 to 6 wt.% of one or more phosphoruscomponents, calculated as P, and (3) calcining the composite produced instep (2) at a temperature of at least 800° F.